CXA1999 SONY [Sony Corporation], CXA1999 Datasheet - Page 12

• Manufacturer Part Number: CXA1999
• Description: IF Amplifier for M-ary FSK Pagers
• Manufacturer: SONY [Sony Corporation]

8) Filter Buffer, Level Comparator and NRZ Comparator
9) REG CONT
10) LVA OUT
11) B.S.
An operational amplifier for LPF is built in this IC.
It is connected internally to the NRZ comparator, level comparator and quick charge circuit.
Using the operational amplifier of Pins 11 and 12 to construct an LPF, remove noise from the demodulated
signal and input the signal to the above three circuits.
The level comparator and the NRZ comparator shape waveform of this input signal and output it as a
square wave. The comparator output stage is for open collector.
Thus, if the CPU is of CMOS type and the supply voltage is different, a direct interface as illustrated in the
figure below can be implemented.
Controls the base bias of the external transistors.
This pin goes high (open) when the supply voltage becomes low. Since the output is an open collector, it
can be used to directly drive CMOS device. The setting voltage of the LVA is 1.05 V (typ.), and it
possesses a hysteresis with respect to the supply voltage. The hysteresis width is 50 mV (typ.).
Operation of the CXA1999N can be halted by setting this pin low. This pin can be connected directly to
CMOS device. The current consumption for battery saving is 20 µA or less (at 1.4 V).
15
(15)
V
14
CC
7
13
4
Comparator output
—12—
L.C.
Fig. 6
Fig. 7
13
0.2V
V
CC
CMOS power supply
1.4V
6
B.S.
12
CMOS IC
11
CXA1999N